Victor Cruz, receiver for the The New York Giants, played Sunday's football game with the boy's name written all over his cleats and gloves.

All the dead children were six or seven-years-old. The school principal, the school psychologist and four teachers were also gunned down.

Addressing the community on Sunday, President Barack Obama said the 20-year-old gunman acted out of "unconscionable evil".

"We bear responsibility for every child ... This is our first task, caring for our children. It's our first job. If we don't get that right, we don't get anything right," he said.

The president's words were heralded by the family of Victoria Soto, 27-year-old Sandy Hook teacher, who wasslain as she tried to protect her first-grade students.

"He really made us feel like she really was a hero and that everyone should know it," Carlos Soto, Victoria's brother, told US broadcaster CBS on Monday.

'Tragedies must end'

Obama, addressing an interfaith vigil in the small Connecticut town on Sunday night, spoke forcefully on thecountry's failings in protecting its children and demanded changes in response to the mass shootings of the last fewmonths.

"We can't tolerate this anymore. These tragedies must end. And to end them, we must change," he said, adding that he would bring together law enforcement, teachers, mental health professionals and others to study how to stop the violence.

In Ridgefield, a town near Newtown, schools were briefly locked down on Monday when police were deployed after reports of a "possibly suspicious person," the school authorities said. The lock down was lifted after two hours when an extensive police search found "no dangerous activity".

Elsewhere in the country, schools across the US opened after the weekend, some put on extra security guards. Others began their day with a moment of silence.

On Twitter, young people nationwide have urged their classmates to wear green and white, the colours of Sandy Hook Elementary School.

In Newtown, schools will not reopen on Monday. The district has said teachers need time to prepare for the students' return.

The town's youth sports groups have set up a field day of sorts to keep children occupied with athletics, board games and arts and crafts.

Al Jazeera's John Terrett, reporting from the centre of Newtown said "the town is trying to get back to where it was ... people are determined" to return to life before the attacks.

The community will also have to make a decision about what to do with the bullet-ridden Sandy Hook Elementary, whosestudents will for now attend classes in an empty school in a neighbouring town.

A more detailed picture of 20-year-old Adam Lanza's attack emerged on Sunday.

Police said Lanza was armed with hundreds of bullets in high-capacity magazines of about 30 rounds each for theBushmaster AR 15 rifle and two handguns he carried into the school, and had a fourth weapon, a shotgun, in his car outside. He killed himself in the school.

Investigators are examining forensic evidence and scouring the crime scene in a process likely to extend for weeks.